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Hepatic lipoate uptake.
J Peinado1, H Sies, T P Akerboom
1Institut für Physiologische Chemie I, Universität Düsseldorf, West Germany.
Archives of Biochemistry and Biophysics
|September 1, 1989
Summary
Hepatocytes actively transport lipoate (LA) via a carrier-mediated process at physiological concentrations. This uptake is temperature-dependent and inhibited by medium-chain fatty acids and acetylsalicylic acid.
Area of Science:
- Hepatobiliary transport
- Nutrient metabolism
- Pharmacokinetics
Background:
- Lipoate (LA) is an essential cofactor in mitochondrial metabolism.
- Understanding hepatic uptake mechanisms is crucial for its therapeutic applications.
Purpose of the Study:
- To elucidate the mechanisms of lipoate uptake in the liver.
- To characterize the kinetics and regulatory factors influencing hepatic lipoate transport.
Main Methods:
- Studied [35S]lipoate uptake in perfused rat liver and isolated rat hepatocytes.
- Analyzed kinetic parameters (Km, Vmax) and temperature dependence.
- Investigated inhibition by various compounds, including fatty acids and drugs.
Main Results:
- Hepatic uptake of lipoate demonstrated saturation kinetics (Km=38 μM, Vmax=180 pmol/mg/10s) at physiological concentrations.
- Uptake was temperature-dependent with an activation energy of 14.8 kcal/mol.
- Medium-chain fatty acids and acetylsalicylic acid significantly inhibited lipoate uptake, while long-chain fatty acids had minimal effect.
Conclusions:
- Hepatic lipoate uptake is primarily mediated by a saturable carrier system at physiological concentrations.
- This transport system is selectively influenced by medium-chain fatty acids and certain drugs.
- Further research into this carrier-mediated uptake is warranted for optimizing lipoate-based therapies.